1. Field of the Invention
This invention relates to hearing aids and more particularly relates to an ear-insertable hearing aid which includes both an acoustic microphone and a magnetic induction pickup.
2. Background
Miniaturization of hearing aids has been a goal for many years. More recently, hearing aids have been miniaturized to where they can be fully inserted into the ear so that the hearing aids are not visible except in a close-up, full profile view of the ear in which they have been inserted.
Another development in the hearing aid field has been to provide a combination microphone pickup and a magnetic induction pickup in the same device. The magnetic pickup or the microphone can be used simultaneously or alternatively. The magnetic induction pickup is normally used to develop an electrical signal from a magnetic flux field, such as the magnetic field of a telephone receiver. With such a device the hearing aid wearer can talk on the telephone and not be troubled by extraneous acoustic sounds. The device also prevents acoustic oscillations which are sometimes caused by the presence of the telephone close to the hearing aid. An alternative use for these induction devices is to assist the hard of hearing when listening to sound reinforcement systems. An example of this type of use is in conjunction with the magnetic field of a conductor loop in a classroom for the hearing impaired. A room (or a portion of it) is surrounded by the conductive loop, through which an electrical signal from a sound reinforcement system passes, creating a magnetic field which is sensed by the magnetic induction pickup. This enables the wearer to hear the sound system without being confused by acoustic reverberation in the room.
Examples of such devices are discussed in U.S. Pat. Nos. 3,396,245, 3,659,056 and 4,912,769. All of the devices discussed in these patents are too bulky to fit completely into the ear of a user.